The recent surge of interest in metal-catalysed C-H bond functionalisation reactions reflects the importance of such reactions in biomimetic studies and organic synthesis. This critical review focuses on metalloporphyrin-catalysed saturated C-H bond functionalisation reported since the year 2000, including C-O, C-N and C-C bond formation via hydroxylation, amination and carbenoid insertion, respectively, together with a brief description of previous achievements in this area. Among the metalloporphyrin-catalysed reactions highlighted herein are the hydroxylation of steroids, cycloalkanes and benzylic hydrocarbons; intermolecular amination of steroids, cycloalkanes and benzylic or allylic hydrocarbons; intramolecular amination of sulfamate esters and organic azides; intermolecular carbenoid insertion into benzylic, allylic or alkane C-H bonds; and intramolecular carbenoid C-H insertion of tosylhydrazones. These metalloporphyrin-catalysed saturated C-H bond functionalisation reactions feature high regio-, diastereo- or enantioselectivity and/or high product turnover numbers. Mechanistic studies suggest the involvement of metal-oxo, -imido (or nitrene), and -carbene porphyrin complexes in the reactions. The reactivity of such metal-ligand multiple bonded species towards saturated C-H bonds, including mechanistic studies through both experimental and theoretical means, is also discussed (244 references).

Selective functionalisation of saturated C–H bonds with metalloporphyrin catalysts

Porphyrin based microporous organic polymer Fe-POP-1 has been synthesized through a facile solvothermal method involving extended aromatic substitution of pyrrole and terephthaldehyde in the presence of Fe(III). This material has very high BET surface area and exhibits two types of catalytic sites: iron-free porphyrin moieties for base catalysis as well as Fe(III)-bound sites for slective oxidation reactions. Due to the presence of basic porphyrin macrocyclic site in Fe-POP-1, it catalyzes Knoevenagel condensation of aromatic aldehydes with malononitrile at room temperature, whereas the Fe(III)-bound site catalyzes selective oxidation of alcohols to the respective aldehyde/ketones in the presence of tert -butyl hydroperoxide (TBHP) as oxidant. Good reusability and excellent selectivity makes this Fe-POP-1 as a promising and efficient bi-functional heterogeneous catalyst for the production of organic fine chemicals through the environmentally benign liquid phase catalytic reactions.

Porphyrin based porous organic polymer as bi-functional catalyst for selective oxidation and Knoevenagel condensation reactions

Hydroxyapatite (HA) is widely used in bone tissue engineering for its bioactivity and biocompatibility, and a growing number of researchers are exploring ways to improve the physical properties and biological functions of hydroxyapatite. Up to now, HA has been used as inorganic building blocks for tissue engineering or as nanofillers to blend with polymers, furthermore, various methods such as ion doping or surface modification have been also reported to prepare functionalized HA. In this review, we try to give a brief and comprehensive introduction about HA-based materials, including ion-doped HA, HA/polymer composites and surface modified HA and their applications in bone tissue engineering. In addition, the prospective of HA is also discussed. This review may be helpful for researchers to get a general understanding about the development of hydroxyapatite based materials.

Hydroxyapatite Based Materials for Bone Tissue Engineering: A Brief and Comprehensive Introduction

A range of talc-like phyllosilicates were prepared via a hydrothermal synthesis performed at five different temperatures from 160 to 350 °C. The organization of the lattice and the degree of crystallinity of the new materials were evaluated by different techniques such as XRD, FTIR, solid-state 29Si NMR, TEM, FEG-SEM and TG-DTA. When synthesized at low temperature the material presents high degree of hydration, low crystallinity and flawed structure. This was attributed to stevensite-talc interstratified product present in the samples. The stevensite/talc ratio and the hydration decrease in the talc-like phyllosilicate samples when the hydrothermal synthesis temperature increases and so the crystallinity becomes higher. A thermal treatment at 500 °C allowed a significant flaw reduction in talc-like phyllosilicate structure; the synthesized sample at 350 °C and heat treated presents a structure close to that of talc. The different talc-like phyllosilicates were grafted covalently by two organoalkoxysilane reagents, N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole (IM2H) and 2-hydroxy-4-(3-triethoxysilylpropoxy)-diphenylketone (HTDK). The grafted amounts of the hybrids, determined by elemental analysis and confirmed by thermogravimetric data, are dependent on the hydrothermal synthesis temperature and organoalkoxysilanes; they become smaller when the synthesis temperature increases and when HTDK is used. FTIR and solid-state 13C CP MAS NMR were applied to characterize the grafted organic groups. So, in this work it is shown that by choosing the hydrothermal synthesis temperature or by performing an additional annealing it is possible to adjust the amount of defects in the structure of talc-like phyllosilicates which seems to be strongly correlated to the grafting performance.

Functionalization of synthetic talc-like phyllosilicates by alkoxyorganosilane grafting

Some features associated with organosilane groups grafted by the sol-gel process onto synthetic talc-like phyllosilicate

FeTFPPCl [5,10,15,20-tetrakis(pentafluorophenyl)porphyrin iron(III) chloride] has been covalently supported on two series of previously aminated phyllosilicates, Tal x (natural) and Sil x (synthesized through sol/gel process), where x (=1–3) represents the length of the organic chain (“arms”) binding the ironporphyrin to the support These systems have been characterized (UV-Vis, IR and EPR) and used as catalysts for the oxidation of alkanes and alkenes by iodosylbenzene and hydrogen peroxide All systems proved to be efficient catalysts for cyclohexane hydroxylation and alkene epoxidation with both oxidants FeTal x are better catalysts than FeSil x for all the investigated substrates The intermediate “arms” of FeTal2 have been the most adequate since they are not short enough to maintain the ironporphyrin near the polar support or long enough to favor axial bis-coordination of the free amino group to the iron center Protection of the excess NH 2 groups through acetylation was essential to prevent such bis-coordination and improve product yields Surprisingly, FeTal x systems have proved better catalysts for such hydrocarbon oxidations with hydrogen peroxide than the homogeneous iron porphyrin

Anchored ironporphyrins—the role of talc-aminofunctionalyzed phyllosilicates in the catalysis of oxidation of alkanes and alkenes

Zn-doped mesoporous hydroxyapatites and their antimicrobial properties

In the present work, the influence of the short-range disorder on the photocatalytic activity of TiO2 nanocrystals obtained by a rapid microwave solvothermal method was evaluated. The synthesis of TiO2 was performed without synthesis additives and with two different capping agents, sodium dodecyl sulfate (SDS) or carboxymethyl cellulose (CMC). Higher short-range disorder was obtained when SDS was used, as indicated by photoluminescence (PL) and also in the Raman spectra. In the second step, TiO2 samples were used as photocatalysts for the degradation of remazol golden-yellow dye (RNL). High efficiency was observed, with meaningful variations in the percentage efficiency depending on the short-range order of the photocatalyst. Our best results were comparable to those of commercial TiO2 Degussa P25. Adsorption isotherms were also evaluated as a function of time, indicating that chemisorption appears to take place, with a high adsorption capacity of the RNL by the photocatalysts.

Photocatalytic and Photoluminescent Properties of TiO 2 Nanocrystals Obtained by the Microwave Solvothermal Method

Two new zinc silicate hybrids were synthesized via sol–gel process from the reaction of zinc ions with trialkoxyaminesilanes in aqueous basic medium at room temperature and at 373 K. The inorganic–organic hybrids obtained, named SILZn (x ¼ 1 or 2) are related to 3-aminopropyl- and N-propylethylenediaminetrimethoxysilane, respectively. From nitrogen content, the number of pendant moles of organic groups in the matrices SILZnx (x ¼ 1 to 2) were determined as 5.14 and 3.25 mmol g � 1 , respectively. The thermogravimetric curves showed mass losses of 50.7% and 58.0% for the same sequence of hybrids, to give the oxides as residue. X-ray diffraction patterns gave basal distances of 2065 and 2814 pm for SILZnx (x ¼ 1; 2), with well-formed particles of irregular shapes and sizes, as a characteristic of such material obtained from sol–gel process. The infrared spectra confirmed the attachment of the organic moieties on siloxane groups on the inorganic framework.

Maria Gardênia Fonseca

Papers

Anchored ironporphyrins—the role of talc-aminofunctionalyzed phyllosilicates in the catalysis of oxidation of alkanes and alkenes

Zn-doped mesoporous hydroxyapatites and their antimicrobial properties

Photocatalytic and Photoluminescent Properties of TiO 2 Nanocrystals Obtained by the Microwave Solvothermal Method

Zinc phyllosilicates containingamino pendant g roups